Carrier pellets, method for production thereof and use thereof

ABSTRACT

The invention relates to a method for the production of carrier pellets for pharmaceutical active substances. Likewise, the invention relates to such carrier pellets and also to pharmaceutical formulations containing these. The carrier pellets according to the invention are used for transporting and releasing pharmaceutical active substances, in particular in the human body.

The present application is a divisional of U.S. patent application Ser. No. 14/209,056 filed on Mar. 13, 2014, which is a continuation of U.S. patent application Ser. No. 12/863,336 filed on Jul. 16, 2010, which claims priority from PCT Patent Application No. PCT/EP2009/000124 filed on Jan. 12, 2009, which claims priority from German Patent Application No. DE 10 2008 004 893.3 filed on Jan. 17, 2008, the disclosures of which are incorporated herein by reference in their entirety.

The invention relates to a method for the production of earlier pellets for pharmaceutical active substances. Likewise, the invention relates to such cannier pellets and also to pharmaceutical formulations containing these. The earlier pellets according to the invention are used for transporting and releasing pharmaceutical active substances, in particular in the human body.

Pharmaceutical administration forms which can be applied in particular orally are intended to be formulated suitably for the respective application in order to effect release of the pharmaceutical active substances at the connect time and without disturbing side-effects. Thus active substances which can be administered for example orally are intended to be released as far as possible such that an unpleasant, e.g. bitter, taste in the mouth is avoided since this can lead to reactions of repulsion in particular in children. On the other hand, the active substances must be released in the stomach or intestine as completely as possible and in a rapidly absorbable form if a systemic treatment is sought.

In the case of oral administration of drugs, the active substance is released in the gastro-intestinal tract and a part of the active substance is absorbed. By controlling the release of the active substance, the degree of absorption and the effective duration can be influenced. Correspondingly, various proposals have been made for controlling release of the active substance by suitable galenic formulations of the active substance.

One approach resides in providing administration forms with coatings, release of the active substance being able to be influenced as a function of the solubility or permeability of the coatings. Such coatings can be applied for example on tablets or capsules. In this case, a disadvantage exists however in that a faulty or damaged coating can lead to the fact that the release of the total active substance dose is not controlled in the desired manner.

There are possible, as an alternative, multipmticulate administration forms in which the total quantity of the active substance is apportioned to a larger number of smaller units, such as pellets. If the individual pellets are provided with coatings, then, in the case of a faulty coating in one pellet, only a correspondingly small proportion of the total active substance dose is not subjected to the desired release.

A further advantage of such administration forms based on pellets resides in the fact that sufficiently small pellets pass into the intestine from the stomach relatively rapidly after ingestion. On the other hand, tablets, as long as they do not disintegrate, can also remain in the stomach for a fairly long time, the time in addition being very variable.

Known administration forms with controlled release are hence not entirely satisfactory. In addition, the problem exists that desired (prescribed) release profiles generally cannot be set. Furthermore, the production of administration forms with controlled release is often difficult. Hence there is a requirement for new administration forms with controlled release and also for new methods for the production of administration forms with controlled release.

It was therefore the object of the present invention to provide carrier pellets and a method for the production thereof, which enable a controlled release of the loaded, pharmaceutically effective component and which do not have the disadvantages of the systems known from the state of the art.

This object is preferably achieved by the characterizing features of the invention. Advantageous embodiments and further developments will be apparent from the description of the invention provided herein.

According to the invention, a method for the production of carrier pellets for an active substance is provided in which:

-   -   a) liquid formulation is produced by dissolving and/or         dispersing at least one physiologically well-tolerated pH         regulator in at least one solvent or emulsifier;     -   b) the liquid formulation is introduced by means of nozzles into         a fluidised bed or spouted bed unit;     -   c) essentially spherical carrier pellets are formed by spray         granulation in the unit in which the solvent is evaporated by         means of a drying gas flow; and     -   d) the carrier pellets are discharged continuously from the         unit.

It is preferred that a pH regulator which has a regulating effect in the physiological surroundings is used, such that the pH value is lowered or increased and hence the bioavailability of pharmaceutically effective components is made possible or increased. This can however also be achieved in that the pH regulator has a stabilising function, e.g. when using a buffer system as pH regulator.

Preferably, the pH regulator is an organic acid, this being selected particularly preferably from the group comprising C₁-C₁₈ mono-, di- and tricarboxylic acids and also mixtures thereof. Representatives of this group, given by way of example, are citric acid, succinic acid, malic acid, fumaric acid, tartaric acid, sorbic acid, adipinic acid, salts and mixtures thereof, it is likewise possible that ascorbic acid or salts thereof are used as pH regulator.

A further preferred embodiment provides that the at least one pH regulator is an acidic or basic salt.

If the pH regulator is a buffer system, then this preferably comprises an acidic or basic salt together with a corresponding caustic solution or acid. Examples of these are citric acid/citrate or tartaric acid/tartrate.

In a further preferred variant, the pH regulator is an organic base, e.g. a purine base or a pyrimidine base, or a mixture of these bases. The purine base is preferably selected from the group comprising adenine, guanine, hypoxanthine, xanthine and mixtures hereof. The pyrimidine base is preferably selected from the group comprising cytosine, uracil, thymine and mixtures hereof.

In the case where the pH regulator is a basic inorganic salt, this is preferably selected from the group comprising NaHCO₃, K₂CO₃, Na₂CO₃, KHCO₃, Ca(OH)₂, CaO, phosphates and mixtures hereof.

Preferably, the formulation contains in addition at least one physiologically well-tolerated binder. This binder is thereby preferably selected from the group comprising methyl celluloses, hydroxymethyl celluloses, hydroxypropylmethyl celluloses, alginates, pectins, polyvinylpyrrolidones, xanthanes and also other hydrocolloids and mixtures hereof.

Preferably water or organic solvents are used as solvents or emulsifiers. As organic solvents, particularly preferred are ethyl alcohol, isopropanol, n-propanol or mixtures thereof.

The quantity ratio of pH regulator to binder in the liquid formulation is preferably in the range of 50:50 to 99:1. A preferred liquid formulation has 30 to 80% by weight of the at least one pH regulator, 0.5 to 5% by weight of the at least one binder and 15 to 69.5% by weight of the at least one solvent.

The spray granulation can be effected both in a fluidised bed unit and in a spouted bed unit. The temperature in these units is thereby preferably in the range of 5 to 100° C. The drying gas flow entering the coating unit has, at the entrance into the unit, preferably a temperature in the range of 5 to 120°. There are possible as drying gas, its particular conditioned air, nitrogen or inert gases, e.g. noble gases.

If the spray granulation is effected in a fluidised bed unit, the drying gas is supplied via a sieve plate. At the same time, the liquid formulation is introduced into the unit by nozzles disposed above the sieve plate.

If the spray granulation is effected in a spouted bed unit, then the drying gas is supplied through longitudinal gaps situated on the bottom. The liquid formulation is introduced via at least one nozzle disposed between the longitudinal gaps.

Preferably, introduction of the liquid formulation is effected through the nozzle from below to above.

According to the invention, likewise carrier pellets which contain at least one physiologically well-tolerated pH regulator are provided. These carrier pellets are produced according to the above-described method.

The carrier pellets preferably have a diameter in the range of 50 μm to 1.5 mm, in particular of 90 μm to 1.2 mm.

The carrier pellets are thereby preferably essentially spherical. The carrier pellets preferably have a sphericity of 0.8 to 1.0, in particular of 0.9 to 1.0.

The sphericity is thereby calculated according to the following formula:

${SPHT} = \frac{4\pi \; A}{U^{2}}$

with A=surface area and U=circumference.

The sphericity can be implemented with devices for particle size- and particle shape analysis with dynamic image analysis. A device suitable for this purpose is for example the CAMSIZER by Retsch Technology.

Furthermore, it is preferred that the ratio of width to length of the carrier pellets is in the range of 0.8 to 1.0, in particular of 0.9 to 1.0. The ratio of width to length is thereby calculated according to the following formula:

${b/l} = \frac{\min \left( x_{c} \right)}{\max \left( x_{Fc} \right)}$

with x_(Fe)=Feret diameter and x_(c)=maximum width of the particle.

Also the width-length ratio can be determined for example with the mentioned CAMSIZER.

Preferably, the carrier pellets according to the invention concern dense carrier pellets, which implies a weight reduction relative to extrusion pellets.

The carrier pellets have essentially the same particle size, i.e. a narrow scatter range with respect to the particle size is present.

The carrier pellets preferably contain at least one physiologically well-tolerated binder. This binder is thereby preferably selected from the group comprising methyl celluloses, hydroxymethyl celluloses, hydroxypropylmethyl celluloses, alginates, pectins, polyvinylpyrrolidones, xanthanes and also other hydrocolloids and also mixtures hereof.

According to the invention, likewise a pharmaceutical formulation is provided, containing the above-described carrier pellets and at least one active substance.

The carrier pellets according to the invention are used as carrier structure for pharmaceutically effective components.

EXAMPLE 1 Production of Dicarboxylic Acid Pellets by Means of D/L Malic Acid

1.1 Production of the Spray Solution

The spray solution comprises purified water, methyl cellulose and malic acid. A 4% binder solution is produced from the purified water and methyl cellulose. This is temperature-controlled at 70° C. Thereafter, the addition of malic acid is effected with constant agitation until a complete solution is present (proportion of purified water corresponds to proportion of malic acid).

1.2 Particle Formation

The temperature-controlled spray solution is sprayed into the spouted bed apparatus (ProCell) in the bottom spray method. A constant particle formation is effected by atomising the solids solution in the main airflow. The latter comprises two partial flows which are produced through gap openings, leading along through the process chamber. The particle construction takes place by evaporation of the solvent water, malic acid and methyl cellulose remain in the airflow dried as particles. By means of the defined flow profile of the apparatus, the particles in the upper process chamber separate from the central airflow and flow laterally, caused by gravity and the suction effect of the main airflow, back towards the process gas inlet. There, they are entrained again with the main airflow and coated continuously with solids from the spray solution. The process air is conditioned.

During the continuous introduction of the solids mixture via atomisation, the removal of acidic pellets is effected at the same time. The malic acid pellets are fractionated for the desired particle size.

Undersize particles and prepared oversize particles can thereby be returned to the process. The end product is a homogeneous virtually spherical malic acid pellet with a uniform surface structure. 

1. A carrier pellet for carrying a pharmaceutically active substance, the carrier pellet comprising at least one physiologically well-tolerated pH regulator, wherein the carrier pellets are produced by the method comprising: a) producing a liquid formulation by dissolving, dispersing, or a combination of dissolving and dispersing at least one physiologically well-tolerated pH regulator in at least one solvent or emulsifier; b) introducing the liquid formulation into a fluidized-bed or spouted-bed unit using at least one nozzle; c) forming essentially spherical carrier pellets by spray granulation in the unit wherein the solvent is evaporated by a drying gas flow; and d) discharging the carrier pellets from the unit.
 2. The carrier pellet according to claim 1; wherein the carrier pellet has a diameter in the range of 50 μm to 1.5 mm.
 3. The carrier pellet according to claim 1; wherein the carrier pellet is essentially spherical.
 4. The carrier pellet according to claim 3; wherein the carrier pellet has a sphericity of 0.8 to 1.0.
 5. The carrier pellet according to claim 1; wherein the carrier pellet has a width-length ratio of 0.8 to 1.0.
 6. The carrier pellet according to claim 1; wherein the carrier pellet is a dense carrier pellet.
 7. A combination of carrier pellets comprising: at two of the carrier pellets according claim 1; wherein at least two of the carrier pellets in the combination have essentially the same size.
 8. A pharmaceutical formulation comprising: one or more carrier pellets according to claim 1; and at least one pharmaceutically active substance.
 9. A method of releasing a pharmaceutically active substance, the method comprising: introducing one or more pharmaceutical formulations according to claim 8 into physiological surroundings, wherein the one or more carrier pellets releases the pharmaceutically active substance into the physiological surroundings. 